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Test of QCD in 2-5 GeV with BESII

Test of QCD in 2-5 GeV with BESII. Weiguo Li, Zhengguo Zhao (Representing BES Collaboration) IHEP of CAS, Beijing, China University of Michigan, Ann Arbor, MI, USA. Final Results of R-values in 2-5 GeV  distribution and 2 nd binomial moment Summary. Experimentally

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Test of QCD in 2-5 GeV with BESII

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  1. Test of QCD in 2-5 GeV with BESII Weiguo Li, Zhengguo Zhao (Representing BES Collaboration) IHEP of CAS, Beijing, China University of Michigan, Ann Arbor, MI, USA • Final Results of R-values in 2-5 GeV •  distribution and 2nd binomial moment • Summary Zhengguo Zhao, Weiguo Li

  2. Experimentally Nhad: observed hadronic events Nbg: background events L: integrated luminosity had: detection efficiency for hadronic events : radiative correction Definition of R R: one of the most fundamental quantities in particle physics, counts directly the number of quarks, their flavor and colors Zhengguo Zhao, Weiguo Li

  3. Reducing the uncertainty of (MZ2) essential for precision tests of the SM Hunting for new physics from a(g-2)/2  Interpretation of E821 at BNL Motivations of the R Scan • Relative contributions to the • uncertainties of a and (MZ2) Zhengguo Zhao, Weiguo Li

  4. Total 91 energy points in 2-5 GeV Single and separated beam collision to study beam associated background Special runs taken at J/, 2.6, 3.0, 3.5 GeV with larger data sample to determine trg L measured by large angle Bhabha LUARLW is developed to improve JETSET for had low energy region, particularly for Ecm< 3 GeV D, D*, Ds, Ds* productions are simulated according to Eichiten Model A generator is built into LUARLW to handle decays of resonances in the radiative return processes e+e-  J/ or (2S) BES’s R Scan Zhengguo Zhao, Weiguo Li

  5. MC Events collected at BESII Data N N Events Recorded by BESII Zhengguo Zhao, Weiguo Li

  6. Tune the parameters to reproduce 14 distributions of the observed kinematic variables and hadronic event shape. Hatched region: MC Histogram: Data Some Hadronic Event Shapes at Ecm=2.2 GeV (LUARLW) Variation of Detection Efficiency and ISR in 2-5 GeV Zhengguo Zhao, Weiguo Li

  7. R Values in 2-5 GeV Zhengguo Zhao, Weiguo Li

  8. R Below 10 GeV Before BES R Scan After BES R Scan Zhengguo Zhao, Weiguo Li

  9. The SM Fit to mH With BES data Without BES data (95% C.L.) (95% C.L.) Zhengguo Zhao, Weiguo Li

  10. Evaluation of s and s(MZ) from R(BES) R(pQCD) and R(BES) Exhibits QCD correction known to O(s3(s)) so far. Precision meas. of R can determine s and thus evaluate s(MZ). Using R at 3.0 and 4.8 GeV, one has: BES: PDG2000: D. Michel pQCD calculation agree amazingly well withBESdata J.H. Kuhn, M.Rreinhauser Nucl. Phys. B619(2001)588 Zhengguo Zhao, Weiguo Li

  11. * MLLA/LPHD fit with BES data  Distribution: =-ln(2p/s) MLLA/LPHD calculations Limiting spectrum when Q0=eff B=a/b, a=11Nc/3+2nf/3Nc2, b=(11Nc-2nf)/3 CF=(Nc2-1)/2Nc=4/3, Nc: quark flavor = 3 nf: # qark flavor produced IB: modified Bessel Function. = 0+ix, where tanh 0 =2 -1, =1-/ BES Preliminary Zhengguo Zhao, Weiguo Li

  12. Average multiplicity: NLO: Multiplicity and Second Binomial Moment BES Preliminary Zhengguo Zhao, Weiguo Li

  13. Summary • BES measured R in 2-5 GeV with average uncertainties of 6.6% (a factor of 2-3 improvement) significant impact on the SM fit: mHiggs moves up from 61 GeV to 90 GeV, up limit from 170 GeV to 210 GeV • R scan data at continuum can be used to test QCD - Preliminary results of  and R2 are consistent with e+e-, ep and N data at high energy. -  consistent with MLLA/LPHD predictions, R2consistent with NLO – 0.07. • CLEOC and BESIII can provide more accurate data at continuum to test QCD at a few percent level. Zhengguo Zhao, Weiguo Li

  14. Error of R Measurement at BESII Zhengguo Zhao, Weiguo Li

  15. Thrust: Mean thrust: 1-T A, B constant Thrust and Mean Thrust BES Preliminary Free para. Zhengguo Zhao, Weiguo Li

  16. Fragmentation function Dqh(x,s) [e+e-(K) + X] are also needed to help determine polarized parton density + K p exp. n N exp. eN exp. * r 20.9 K / p 20.9 K/ BESII(3.0) preliminary 0.15 0.20 0.25 0.30 0.35 0.40 0.45 S/U [e+e-(K) + X] and Fragmentation Function, S/U Ratio S/U: input parameters in hadron production generatorneeded for determining h Zhengguo Zhao, Weiguo Li

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